--------------------
* Remove bundled echo package and list as a dependency. [2125]
* Add the ability to export Python scripts for the profile viewer. [2082]
* Add support for polar and other non-rectilinear projections in
2-d scatter viewer [2170]
* Add legend for matplotlib viewers (in qt and in export scripts) [2097, 2144, 2146]
* Add new registry to apply in-place patches to the session file [2127]
* Initial support for dask arrays. [2137, 2149]
* Don't sync color and transparency of image layers by default. [2116]
* Python 2.7 and 3.5 are no longer supported. [2075]
* Always use replace mode when creating a new subset. [2090]
* Fixed bugs in the profile viewer that occurred when using the profile viewer and
setting reference_data to a different value than the default one. [2078]
* Updated the data loader to be able to select directories. [2077,2080]
* Move spectral-cube data loader to glue-astronomy plugin package. [2077]
* Show session filename path in window title. [2096]
* Change ``Data.coords`` API to now rely on the API described in
https://github.com/astropy/astropy-APEs/blob/master/APE14.rst [2079]
* Update minimum required version of Astropy to 4.0. [2079]
* Added a ``DataCollection.clear()`` method to remove all datasets. [2079]
* Fixed a bug that caused profiles of subsets to not be hidden if an
existing subset was emptied. [2095]
* Improved ``IndexedData`` so that world coordinates can now be shown. [2081]
* Make loading Qt plugins optional when calling ``load_plugins``. [2112]
* Preserve ``RectangularROI`` rather than converting them to ``PolygonalROI``. [2112]
* Significantly improve performance of ``compute_fixed_resolution_buffer`` when
using linked datasets with some axes uncorrelated. [2115]
* Improve performance of profile viewer when not all layers are visible. [2115]
* Fixed missing .units on ``CoordinateComponent``. [2117]
* Improve auto-linking of astronomical datasets with WCS information. [2161]
* Fix bug that occurred when using the GUI link editor when links had
been defined programmatically. [2166]
* Add the ability to programmatically set the preferred colormap for a
dataset using ``Data.visual.preferred_cmap`` [2131, 2168]
* Fix bug that caused incorrect unit to be shown on slider for images. [2159]
* Improve performance of ``Data.compute_statistic`` for subsets. [2147]
* Fix a bug where x_att and y_att could end up being out of sync in image viewer. [2141]